The invention relates to an improved whole-blood or isolated red blood cell diagnostic test for diagnosing or predicting various inflammatory and other conditions.
Erythrocyte sedimentation rate (ESR) is a simple diagnostic test which determines the distance red blood cells in a sample of anticoagulated whole blood settle in one hour, and is expressed in units of mm per hour. This test measures the acute phase response to inflammatory disease. The current ESR test is similar to that described by Fahraeus (1921, The suspension-stability of the blood. Acta Med Scand 55:1-228) and Westergren (1921, Studies of the suspension stability of the blood in pulmonary tuberculosis. Acta Med Scand 54:247-282) in 1921, and has changed little since that time. The International Council for Standardization in Hematology (ICSH) has more recently put forth its description for the Erythrocyte Sedimentation Rate (ESR; Bull B S, Caswell M, Ernst E et al. ISCH recommendations for measurement of erythrocyte sedimentation rate. J Clin Path 1993, 46:198-203). The standardization method describes blood sample collection, anticoagulation, dilution of sample, sedimentation pipette and holding device specifications, calculating result and verification. The anticoagulant blood is drawn into a long tube with a narrow uniform bore. After placement of blood in the tube, the lower end is sealed, the tube placed in a vertical position and the distance (usually mm) the erythrocytes settle in 1 hour recorded as the ESR. Normal values are considered to be 15 mm or less. Automatically-zeroing ESR tubes are available as well as automatic instrumental determination of ESR values.
The ESR is a nonspecific marker of the inflammatory process and appears simplistic in concept. That is, cells and plasma interact under the influence of gravity and the final sedimentation distance of cells at one hour can be measured by simply reading the graduated tube. Beyond diagnosis of inflammatory diseases per se, reports describe the use of ESR in monitoring sickle cell disease, osteomyelitis, stroke, myocardial infarction, cancer, pregnancy, infection, atherosclerosis, rheumatoid arthritis, ischemic heart disease and trauma.
However, the major problems with the ESR are that it (1) is a nonspecific marker for disease; (2) it has lack of sensitivity in some disease states, and (3) it is rarely elevated in asymptomatic individuals, who may have occult disease. It is towards improving the value and utility of the ESR test and increasing its sensitivity for the diagnosis, monitoring and prognostication of various conditions and diseases that the present invention is directed.
The citation of any reference herein should not be construed as an admission that such reference is available as xe2x80x9cPrior Artxe2x80x9d to the instant application.
In its broadest aspect, the present invention is directed to a method for determining the health status of an animal, preferably a human, by carrying out the sequential steps of: (i) obtaining an anticoagulated sample of whole blood from the animal; (ii) determining at least one erythrocyte sedimentation rate (ESR) of the sample in the presence of at least one ESR-modulating agent; and (iii) correlating the at least one ESR in the presence of the at least one ESR-modulating agent with the health status of the animal. The health status may indicate presence or extent of a condition or disease, propensity for the development of a condition or disease, or effect of therapy on a condition or disease, such as, but not limited to, inflammation, sickle cell disease, osteomyelitis, stroke, myocardial infarction, cancer, pregnancy, infection, atherosclerosis, rheumatoid arthritis, ischemic heart disease and trauma. It may also help decide on the course of therapy of a particular disease or condition, such as whether the cardiac patient is a candidate for an angioplastic procedure or will need a more invasive surgery such as a bypass operation.
The foregoing modified ESR determination may also be performed in combination with at least one other assay, such as but not limited to clotting time or a metal- or polymer-modified clotting time, to provide data of additional diagnostic or prognostic utility. Other additional tests include red blood cell deformability and any other clotting parameter, as traditionally done or as modified by the addition to the blood sample of a modifying agent such as a metal ion, polymer, or other agent as described herein.
By way of non-limiting examples, the ESR-modulating agent may be a metal ion, such as silver, mercuric or lanthanum ion; a polymer, such as methylcellulose or polyvinylpyrrolidone; epinephrine; an oxidant such as hydrogen peroxide; a procoagulant such as but not limited to a snake venom, such as Russell""s viper venom; an endotoxin; or collagen.
In a further embodiment, the above method may be carried out with an additional ESR determination is performed on the sample in the absence of an ESR-modulating agent. In another embodiment, an additional ESR determination is made on the sample in the presence of a second ESR-modulating agent. All of the foregoing methods may be performed on washed erythrocytes (red blood cells) rather than anticoagulated whole blood. They may be washed or isolated in plasma, albumin solution, normal saline, etc.
The anticoagulated sample of whole blood may be anticoagulated with, for example, citrate, isocitrate, heparin or EDTA.
The prognostic value of the present invention includes, among other uses, determining from a sample of blood whether a cardiac patient will be a candidate for an angioplastic procedure, or may need more extensive surgery such as a bypass operation. This may be achieved from the modified ESR determination, optionally in combination with at least one additional determination, such as a modified clotting time. In one embodiment, a whole blood sample is drawn, anticoagulated, and a modulator such as a silver (I) or mercury (II) salt, or a polymer such as methyl cellulose, is added to the sample. The sample is divided into two aliquots. With one aliquot, a gravity erythrocyte sedimentation rate is determined. With the other sample, a calcium salt is added and the clotting time is determined. From the results of the modified ESR and modified clotting time, prognosis as to the likelihood or risk of acute or chronic coronary heart disease may be made. In a patient presenting with acute chest pain, the test aids in determining whether an angioplastic procedure may be useful or whether the patient should be prepared for a coronary artery bypass graft procedure.
Therefore, it is an object of the invention to improve the diagnostic specificity of an erythrocyte sedimentation rate (ESR) determination by performing the ESR determination in the presence of an ESR-modulating agent, optionally along with at least one additional whole blood test.
These and other aspects of the present invention will be better appreciated by reference to the following Detailed Description.
Improvements have been made herein in the methodology of performing the erythrocyte sedimentation rate (ESR) so that many of its defects can be removed, and moreover its sensitivity may be increased to expand its diagnostic and prognostic value. The test is extremely simple to perform, and can be done on an anticoagulated whole blood sample present in a capillary or other similar tube, wherever a source of gravity is present. While instruments can help automate the determination and perhaps increase the speed of the test (from the usual prescribed one hour of settling), the basic test is applicable to a wide variety of conditions and locations, including medical facilities with minimal equipment and personnel, military or battlefield conditions, as well as in space. Alternate gravity conditions will of course require recalibrating the ESR, but the improvements described herein are applicable to the ESR test wherever and however it is normally performed. The various aspects of the invention applicable to human blood are equally applicable to the blood of non-human animals, such as domesticated animals, wild animals, and animals raised for food and other products.
The main aspect of the invention is the surprising and unanticipated finding that the addition of various agents to the blood sample alters the value of the ESR and moreover, the ESR value of the blood with the addition of the agent or agents (hereinafter referred to as the xe2x80x9cmodified ESRxe2x80x9d) is of improved diagnostic value in identifying abnormalities, i.e., samples from individuals with a condition or disease, and furthermore, the magnitude of the severity of the condition or disease. The modified ESR also permits more sensitive monitoring of conditions during their early, occult or covert stages, at stages where no other detection method is useful, during progression or treatment, as well as permitting the early identification of conditions or disease which have not yet manifest in the form of symptom or syndrome, or exhibiting an altered traditional ESR value. The modified ESR can be used to rule in or rule out certain conditions or diseases. It can also help guide the course of treatment. Thus, the modified ESR improves upon all of the uses of the traditional ESR test.
The improvements provided by the instant invention are manifold. It is great boon in countries of lower economic capabilities, where diagnostic facilities have limited personnel and equipment. It can be performed by lesser trained laboratory staff or others. It is a great aid in the in-vitro and in-vivo testing of drugs and therapies. It is a prognostic indicator for surgical, pharmaceutical or other modes of disease treatment or prevention. It can be performed simply in remote locations, such as in polar field stations or during space travel, to monitor health status and gain an early indication of need for medical intervention.
In addition, the modified ESR test described here may be performed in conjunction with other tests on whole blood, perhaps as simple as the ESR test, to increase the diagnostic and prognostic value of the modified ESR test. For example, a calcium-activated clotting time (recalcification time) can also be performed on the same anticoagulated blood sample. Any whole blood coagulation instrument may be used to perform the at least one additional test, such as may be performed using a Sonoclot Coagulation Analyzer, Thrombelastograph, Hemocron 801, Sigma KC4A, Diagnostica Stago ST4, or any other related instrument. As noted above the at least one other whole blood test may be performed as generally and traditionally done in the hematology test setting, or it may be a modified test such as a metal-ion- or polymer-modified whole blood test, such as a modified clotting test described in U.S. Pat. Nos. 6,245,573; 5,792,660; and 5,783,447, to name but a few non-limiting examples where additional reagents are added to a traditional hematologic test to obtain additional and useful data that may be diagnostic or prognostic as to a disease or condition.
By way of non-limiting example, a method for the manual determination of the modified ESR may be carried out as follows. To 900 microliters of human citrated (or isocitrate, EDTA, heparin or other anticoagulant) whole blood (CWB) in a plastic vial was added 100 microliters of test vehicle or test reagent dissolved in vehicle. The samples are capped, incubated at 37 degrees Celsius for 10 minutes and then the samples were added to sedimentation rate tubes and the ESR determined at varying time intervals. The ESR is defined as the distance traveled by the erythrocytes (red blood cells under the influence of [1xc3x97 g] gravity). Unless noted otherwise, the ESR values reported are those determined at the traditional time, one hour.
As described herein, various reagents may be added to the anticoagulated whole blood sample to provide the modified ESR determination. Numerous such reagents in several classes have been found to alter ESR and provide diagnostically-useful information. These agents generally include (1) metal ions, such as but not limited to silver, mercuric and lanthanum ion; (2) polymers, such as but not limited to methylcellulose and polyvinylpyrrolidone; (3) epinephrine; (4) oxidants, such as but not limited to hydrogen peroxide; (5) a procoagulant agent such as a snake venom, such as but not limited to Russell""s Viper Venom; (6) endotoxins, such as but not limited to Gram-positive endotoxin and Gram-negative endotoxin (LPS); and (6) collagen; to name but a few examples of such compounds. Each of these groups will be elaborated on in more detail below. Criteria for the selection of such reagents may include one or more of the following: toxic to cells; membrane altering; alters solvent properties; reacts with protein, lipids, DNA, or RNA; cellular or plasma distorter, e.g., pH, ionic strength, viscosity, alter electrostatic or other factor to potentiate cellular interactions or inhibit same; and generate more or less effective cellular collisions, cellular adhesion, lysis; and generate, or prevent generation of above-type compounds.
The preferred modulator of ESR rate is a metal ion, such as silver (I), mercury (II), lanthanum (III); lead (II), cadmium (II), tin (I), iron (III), copper (II), cobalt (II), nickel (II), zinc (II), cerium (III), magnesium (II), calcium (II), chromium (III), lutetium (III), scandium (III), thallium (III), ytterbium (III), thorium (IV), and uranate (II). Silver (I) and mercury (II) are preferred. These may be included in the anticoagulated whole blood at level of about up to mM concentrations. Methylcellulose (MC) may be included at about 0.1%.
Other agents include polymers, such as but not limited to methylcellulose and polyvinylpyrrolidone; epinephrin (ADRENALINE(copyright)); oxidants, such as but not limited to hydrogen peroxide; snake venoms, such as procoagulant snake venoms including but not limited to Russell""s Viper Venom; endotoxins, such as but not limited to Gram-positive endotoxin and Gram-negative endotoxin (LPS); and collagen. Others include tissue factor, prothrombotic venoms, thrombin, platelet activating factor, fibrinogen, kaolin, celite, adenosine diphosphate, arachidonic acid, collagen, and ristocetin. Factors with anticoagulant activity useful as modulators of the clotting process of the present invention include protein C, protein S, antithrombin III, thrombomodulin, tissue plasminogen activator, urokinase, streptokinase, and Von Willebrand Factor. Addition of therapeutic drugs which may modulate the coagulant activity of blood may also be used as modulators in the present invention. In addition, cancer cell extracts and amniotic fluid may be used.
As will be seen in the examples below, the prognostic value of a combination of the modified ESR and modified clotting time is useful in determining whether a cardiac patient presenting with severe chest pain is a candidate for an angioplastic procedure, such as balloon angioplasty, or upon catheterization prove to have disease too advanced for angioplasty and would therefore be a candidate for CABG or other procedure. Significant time, health care costs, and importantly, morbidity and mortality could be reduced if such a determination could be made and the appropriate procedure performed immediately. The present modified ESR test, optionally in combination with a modified clotting time, serves this function.
The present invention may be better understood by reference to the following non-limiting Examples, which are provided as exemplary of the invention. The following examples are presented in order to more fully illustrate the preferred embodiments of the invention. They should in no way be construed, however, as limiting the broad scope of the invention.